This invention relates to engine mounting devices for motorcycles, and more particularly it is concerned with an engine mounting device for a motorcycle having a serrated belt or a chain trained over a drive sprocket wheel supported on one side of an engine and a follower sprocket wheel supported on a rear wheel, the engine mounting device comprising support rods connected to an extending crosswise of a motorcycle body for supporting an engine body through cylindrical vibration absorbing rubber members and bushes.
When a motorcycle provided with this type of engine mounting device is suddenly started, the engine body is strongly pulled rearwardly of the motorcycle body by the tension of the serrated belt or chain to force a rear portion of each vibration absorbing rubber member to be radially compressed, so that the engine body might be biased rearwardly to reduce the distance between the drive sprocket wheel and the follower sprocket wheel. When this is the case, particularly when the serrated belt is in use, the serrated belt might be brought out of meshing engagement with the teeth of the sprocket wheels and the phenomenon of random meshing of the teeth might occur, thereby shortening the service life of the serrated belt. Even when a chain is used, loosening of the chain might occur. Also, the vibration absorbing rubber members might be liable to damage due to excessive compression.
Proposals have hitherto been made to obviate this problem by providing a vibration absorbing rubber member higher in hardness than the aforesaid fibration absorbing rubber members to the vicinity of the drive sprocket wheel to thereby regulate the amount of rearward movement of the engine body. However this solution has proved unsatisfactory because the difference in the hardness of the type of vibration absorbing rubber members has resulted in a reduction in the effects achieved in absorbing vibration. If the two vibration absorbing rubber members have the same hardness to avoid this reduction in the effects achieved in absorbing vibration, it becomes impossible to positively regulate the amount of rearward movement of the engine body.